1. Field of the Invention
This invention relates to the field of animal feed and animal nutrition. This invention relates primarily to the field of nutrition for ruminant animals, especially dairy cows. There is a constant need to improve the economical feeding of such animals to maximize the availability of nutrients (and often milk production), and to minimize the factors reducing animal growth and the quantity and quality of milk production.
2. Background Information
Ruminant animals, especially dairy cows, often experience reduced milk production during early lactation. Such depressed milk production is believed to be the result of the decreased supply of protein to the small intestine and the general diversion of energy accompanying lactation. These results are believed to be attributable to inefficient rumen microbial functioning caused, at least in part, by the ruminant's inability to maintain a desired microbial population that provides a desired flow of nutrients to the lower gut. To counteract such reduced milk production, the dairy industry has traditionally overfed protein and/or supplemented the ruminant diet with high levels of undegradable protein. However, unless sufficient energy is also supplied, overfeeding protein is often wasteful because it may result in the loss of unused ammonia nitrogen. Supplementing the diet with high levels of undegradable protein is often cost prohibitive.
Non-structural carbohydrates that are readily fermented in the rumen can be added to the diet to increase the utilization of ruminal ammonia nitrogen for microbial protein synthesis. (Casper & Schingoethe, J. Dairy Sci., 72:928 (1989); Schingoethe et al., J. Dairy Sci., 66:2515 (1983).) Such soluble sugars probably provide rumen microbes with energy for synthesizing protein using ruminal ammonia nitrogen; if adequate energy is not available for such microbial growth and protein synthesis when the ruminal ammonia is available, much of the ammonia nitrogen remains unused and is eventually lost as urea. Feeding whey, containing lactose, stimulates total ruminal microbial protein synthesis, particularly by the bacteria of the rumen. (Winschitl et al., J. Dairy Sci. 67:3061-3068 (1984).)
One concern with the feeding of high levels of soluble sugars, such as lactose, to a ruminant is the accumulation of lactic acid in the rumen. Lactic acid is produced from the fermentation of carbohydrates by the rumen microbes. High levels of lactic acid in the rumen tend to lower rumen pH, leading to laminitis and digestive upset caused by acidosis in the rumen. It has recently been shown that supplementing the ruminant diet with malic acid and fumaric acid increases the uptake and utilization of lactic acid by ruminal bacteria such as Selenomonas Ruminantium. (Nisbet et al., J. Anim. Sci., 72:1355-1361 (1994); Nisbet et al., Current Microbiology, 26:133-136 (1993).)